As for a device attached to an upper end of a filler pipe (also called an inlet pipe and the like), and opening by an insertion of a fuel filling nozzle of a fuel filling gun so as to feed fuel, there are devices shown in Patent Documents 1 and 2.
The device of the Patent Document 1 includes an upper valve member pushed to open by the fuel filling nozzle, and a lower valve member. Thereby, a screw-type fuel inlet cap is unnecessary. However, the valve member of the Patent Document 1 has a structure of turning around one axis, so that a space for allowing turning to an open position of the valve member which is necessary below the valve member cannot be minimized.
On the other hand, in the device of the Patent Document 2, a dust flap is formed by a pair of semicircular flaps, and each flap has a structure turnably supported in a portion opposite to a portion abutting against the other flap in a closed position so as to minimize a space for allowing the flap to turn to an open position which is necessary below the flap. However, in a case wherein such dust flap is simply formed by the pair of semicircular flaps, when both of the pair of flaps or one of the pair of flaps slightly shift or shifts to a position in a shaft center line direction of a turning shaft thereof, there is a possibility of reducing a sealing performance of the flap.